code: def test_merge_known_to_single(
      df_left,
      df_right,
      ddf_left,
      ddf_right_single,
      on,
      how,
      shuffle_method,
  ):
      # Compute expected
      expected = df_left.merge(df_right, on=on, how=how)
  
      # Perform merge
      result = ddf_left.merge(
          ddf_right_single,
          on=on,
          how=how,
          shuffle_method=shuffle_method,
      )
  
      # Assertions
      assert_eq(result, expected)
      assert result.divisions == ddf_left.divisions
      assert len(result.__dask_graph__()) < 30
  
imports: from __future__ import annotations
  import numpy
  import pandas
  import pytest
  import dask.dataframe
  from dask.dataframe._compat import PANDAS_GE_210
  from dask.dataframe.utils import assert_eq
label_desc: Use image node_id 14 for calling a global function with example usage: test_merge_known_to_single(df_left, df_right, ddf_left, ddf_right_single, on, how, shuffle_method) without return types